Microreactor is a flow type reaction apparatus in which chemical reactions take place in a space (microchannel) with the size of 1 mm or less per one side. Compared to the typical large scale reaction apparatus, in the microreactor, the heat caused by the exothermic reaction can be removed rapidly and the temperature distribution bias can be prevented, because the heat-transfer efficiency is high. Further, expansion to inductrial production is easy since the microreactor can be scaled-up by increasing the number of microchannels in the industrial process.
A microreactor can be manufactured by, for example, forming a groove as a flow channel on a flat substrate by a photolithographic method and covering the flat substrate formed with the groove using a flat plate, the flat plat being provided with a raw material introduction port and a product discharge port (for example, Patent Document 1). Flow channels can be classified into T-shaped, J-shaped, Y-shaped, cyclone-shaped and pillar-shaped flow channels. The microreactor is placed so as to keep the flow channel in a horizontal position, and the chemical reaction takes place in the horizontal flow channel (microchamber).
Meanwhile, the utilization of the microreactor in the gas-phase chemical reaction has a long history and plenty of studies have been made. However, the utilization of microreactor in the liquid phase chemical reaction has a shorter history and many problems remain. For example, in the liquid phase chemical reaction in the microreactor, pressure loss is large and clogging may occur. Furthermore, in a reaction system in which gas is generated by the reaction, since the gas extrudes the contents, an expected reaction time cannot be retained, or since the gas adhere to the surface of the catalyst, contact between the raw material and the catalyst is inhibited, thereby making it impossible to increase the reaction rate.
In order to enlarge the contact area between the catalysts and the reaction raw material in a chemical reaction reactor, a catalyst having a large specific surface area is usually used. For example, a catalyst in which a granular support having a smaller size than the inner diameter of the chemical reaction reactor carries a metal catalyst can be cited as an example. However, when a liquid phase reaction is conducted in a microchamber filled with the granular solid catalysts, channeling (a phenomenon in which an unexpected thick flow channel is formed in a catalyst-filled layer and the raw material fluid only flows into the unexpectedly formed flow channel, and does not flow into other flow channels.) occurs. Therefore, the contact area between the reaction raw material and the catalysts may becomes smaller than the designed value and the reaction rate may become lower.
[Patent Document 1] Japanese Unexamined Patent Application, First Publication No. 2007-136345